I. Technical Field
The present invention relates to a seal member which is composed of a double-structure bellows and is provided between a casing and a bearing in a nuclear steam turbine that generates power by rotating a rotor using steam. The present invention also relates to a steam turbine and a method of avoiding resonance.
II. Description of the Related Art
In a typical steam turbine, an inner casing is provided inside an outer casing, wherein a steam inlet portion is provided in an upper part. A rotor is rotatably supported in a central part, and the rotor has a plurality of stages of rotor blades fixed thereto. At the same time, a plurality of stages of nozzles are fixed to a turbine diaphragm supported in the inner casing such that they are arranged alternately with the rotor blades fixed on the rotor.
Thus, during operation of the steam turbine, steam that has entered the inner casing from the steam inlet portion flows through the nozzles supported on the turbine diaphragm via a partition wall and hits the rotor blades, thereby rotating the rotor to drive a generator connected to this rotor.
In the steam turbine, the rotor, which is a rotating member, is supported by bearings in a rotatable manner, and the bearings are supported on a foundation made of concrete or the like of the steam turbine. A gland part is supported using a bearing base and its connecting part that are supported on the foundation. A corrugated pipe called bellows, which is movable seal means, is used to seal between the gland part and the casing. The bellows absorbs displacement between the casing and the gland part caused by thermal expansion of the casing, as well as prevents vibration of the combustion engine from being transmitted (see, Japanese Patent Application Laid-Open No. Hei 10-141565 and Japanese Patent No. 3831617).